The present invention refers to an arrangement for random selection of one among a plurality of devices which are marked as selectable by the condition of marking wires in a telecommunication system by means of a selecting chain consisting of a number of selecting circuits each connected to its own line, activation of a selecting circuit in the selecting chain preventing activation of other selecting circuits belonging to the chain in order to prevent that upon simultaneous call of several selecting circuits in the selecting chain that one of the selecting circuits which due to the characteristics of its components is most rapid always is selected first. The problem which has to be solved is consequently to prevent an uneven load and a rapid wear of the devices which are selected more often. Furthermore it is necessary to secure that only one device can be selected at the same time.
In previously known solutions, for example the Swedish Pat. No. 302 791, a special kind of selecting chain is used in order to secure that only one device can be selected at the same time. This method does not, however, result in random distribution in view of the selection of the devices and the problem of uneven load of the devices is still not solved.
According to the Swedish Pat. No. 182 638 an automatically stepping selecting chain is used which is built up of monostable flip-flops. The drawback with this arrangement is, however, that it steps forward with a constant velocity and there is a risk that after a long sequence of busy marked devices a certain idle device has priority compared with the others.
According to the invention said problem is solved. The invention is defined in the enclosed claims.